Resistance unit



March 10, 1931. H. F. GILL RESISTANCE UNIT Filed Feb. 26, 1929 PatentedMar. 10, 1931 UNITED STATES PATENT OFFICE.

HARRY F. GILL, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR '10 WIRT COMPANY,01? PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF MAINE nnsrs'mncn om'rApplication filed February 26, 1929. Serial No. 342,881.

My invention relates to electrical devices and methods of manufacturingthe same, and it has for one object the provision of a resistorparticularly adapted for use in radio receivers that shall becharacterized by its simplicity of design, ease of construction, anddesirable operating characteristics.

Another object of my invention is to pro Vide an electrical resistancedevicecomprising an insulating member, a coil of wire mounted thereon,and a plurality of terminal connections connected at spaced intervals tothe coil, said terminal connections being characterized by their lowmanufacturing cost, and by the ease with which they may be assembled inresistor units of the character described. V

A further object of my invention is to provide means, whereby theexposed surface of a conductor may be protected in a simple andefficient manner,my invention contemplating in particular the provisionof a protective surface covering formed of an insulating thread.

A still further object of my invention is to provide electricalapparatus, comprising a coil of wire having an insulating surfacecoating, a protective covering for the surface coating formed of athread of insulating material, and an exterior surface coating for saidthread covering.

With these and other objects and applications in mind, my inventionfurther consists in the details of construction, operation, andarrangements, hereinafter described and claimed and illustrated in theaccompanying drawing, wherein Fig. 1 is a side elevational view of atapped resistor unit embodying my invention;

Fig. 2 is a view similar to'Fig. 1, but showing certain portions of theresistor unit broken away; and

Figs. 3 and 4 are transverse sectional views taken on the lines 3-3 and44, respectively, of Fig. 1. I

Referring to the drawing, the tapped resistor unit 1 therein showncomprises a tubular core or support 2 of insulating material which isprovided with intermediate and end terminal connections 3 and 4,respectively. Each. of these terminal connections comprises a circularportion 5, which closely fits an outer side 6 of the insulating tube 2,and a pair of end portions 7 and 8.

The end portions 7 and 8 are fastened together by means of a struck-uptongue 9 which extends from the end portion 8 through a recess 11 in theend portion 7. As shown in Fig. 3, an end 12 of the tongue 9 is foldedaround and adjacent edge portion,13, so that the end portions 7 and .8may be rigidly interlocked. One of the end portions 7, 8, say theformer, is provided with an extension 14 having a slot 15 which extendsinwardly from one edge thereof, whereby a hook 16 may be formed. Thus, alead wire (not shown) may be readily secured to the terminal connectionmerely by being wound or looped around the hook 16.

A wire coil 18 is wound around the insulating tube 2, and it isconnected at intervals to the terminal connections by being loopedaround a pair of oppositely extending hooks 19 and 21. As illustrated inFig. 3 the books 19 and 21 are formed in the curved portion 5 of theterminal connections by pressing outwardly adjacent portions thereof,preferably during the stamping operation.

The outer surface of the wire coil 18, the terminal connections 3 and 4,and the exposed (portion of the insulating tube 2-are covere first witha. suitable insulating coating 22 and then with a coating 23 consistinglargely of an asphaltic material. Since the coating 23 is very brittle,it frequently happens that the resistors are rendered useless by reasonof the chipping of the coating 23 from the wires, thereby permittingthe, short-circuiting thereof. This difficulty is overcome in myinvention by providing an insulating protective covering for the wirecoil 18 and the brittle coating 23, which prevents injury to the coating23, as well as the wire coil 18, in the event, for example, that aperson handling the resistor unit 1 should strike the same with a toolor other sharp object. o

The insulating protective covering, in accordance with my invention, isformed by winding a fine thread 24 of cotton or other insulatingmaterial spirally over the Wire coating 23, as shown in Fig. 2. Suchcovering-"- may be readily applied to the resistor unit 1 with a minimumexpenditure of time and I of money, andafiords maximum protection.Preferably, the thread coveringis provided with a coating 25 of suitableinsulation material, such as asphaltic material. p

In practice, the method of manufacture involves first the formation ofthe 'terminal the said helically coiled cotton string.

In testimony that I claim the foregoing as my invention I have hereuntosigned my name this 23d day of February A. D. 1929. HARRY F. GILL.

connections'3 and 4, and then the mounting of these connections on thetubular member 2. The wire coil 18 is next wound on .the tube 2 andconnected at intervals to the ter+ minal connections 3 and 4:. The wholeis now placed in a bathof suitable insulating material such as asphalticmaterial so as to insulate the coils of wire from one another andeffectively secure the same in position, whereupon the asphalt coating23 is applied.

In accordance with my invention, the next step consists in winding thethread of cotton or othevinsulating material around the coating 23, asshown in Fig. 1, in order to form the thread covering, whereupon theunit is again dipped in a bath of asphaltic material, to form theoutside protective coating 25. The final product represents a re sistorunit which may be subjected to rough handling, such as frequently occursin course of transit, with substantially no danger of injuring the innerprotective coating 23 or causing the short-circuiting of the turns ofthe wire coil 18; v

While I have shown only one form of embodiment of my invention, for thepurpose of describin the same and illustrating its principlesconstruction and operation, it is apparent that various changes andmodifications may be made therein, without departing from the spiritofmy invention.

. Having thus described my invention, what I claim and,desire to secureby Letters Patent is:

1. An electrical resistance device comprising a support of insulatingmaterial, a,-con-' ducting wire wound helicallyaround said support, theadjoining helixes of the said wire being insulated from each othe'r,-acoating of b, asphaltic material overlying the said helically woundwire, a string-of fibrous mate rial helically coiled around the saidcoating, and a protective coating of asphaltic material overlying thesaid helically coiled string. 7 J

2. ,An electrical resistance device comprising a tubular support'ofinsulating material, an electric conductingwire helically coiled aroundthe said support, the adjoining helixesv of the said-wire beinginsulated from: each other, an insulating fibrous material overlying thesaid helically coiled conducting. wire, 'and. 'asphaltic materialimpregnating and overlying the said fibrous material; B5-:3.Ai1-e1ectrical.. 1' esistance device .compris:

I no

